Flexlink is a pair of a Layer 2 interfaces such as switchports or port channels, where one interface may be configured to operate as a backup interface to the other interface. This approach provides an alternative option to the Spanning Tree Protocol (STP) by allowing the users to turn off STP and still retain basic network link redundancy. Flexlinks are generally configured in service provider or enterprise networks where it is not desirable to run STP on the network switch. Indeed, STP is disabled on flexlink interfaces. Flexlinks also provides faster convergence than STP.
Generally, flexlinks may be configured on one Layer 2 interface (the active link) by assigning another Layer 2 interface as the flexlink or backup link. When one of the links is up and forwarding traffic, the other link is configured on standby mode, ready to begin forwarding data traffic if the other link shuts down. At any given time, only one of the interfaces is forwarding data or traffic. If the primary link shuts down, the standby link starts forwarding traffic, and when the active link comes back up, it goes into standby mode.
In general, only one flexlink backup link may be configured for any given active link, and is a different interface from the active interface. Also, an interface can be associated to only one flexlink pair—that is, an interface may be configured as a backup link for only one active link in the network, and further, an active link cannot belong to another flexlink pair.
More over, neither of the active and backup links forming the flexlink pair can be a port that belongs to an EtherChannel (but two port channels (e.g., EtherChannel logical interfaces) may be configured as flexlinks, and a port channel and a physical interface may be configured as flexlinks with either the port channel or the physical interface as the active link. Additionally, the backup link does not have to be the same type (for example, Fast Ethernet, Gigabit Ethernet, or port channel) as the active link. However, to minimize the potential for loops or changes in behavior if the standby link begins to forward traffic, it is desirable to configure both flexlinks with similar characteristics.
Notwithstanding, configuration of flexlink feature is error prone, and trivial configuration or cabling errors leads to loops which may lead to network meltdown. Moreover, minor procedural errors can generate a lock out, and each network device has different subtle limitations is constraints, thus making the flexlink configuration procedure challenging.
In view of the foregoing, it would be desirable to have methods and systems for providing automatic configuration of flexlink feature in a data network which is automatically turned on and/or based on dynamic changes to the network topology.